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Mortgage servicing rights - Data and Key Economic Assumptions Related to Mortgage Servicing Rights (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Transfers and Servicing of Financial Assets [Abstract] |  |
Unpaid principal balance | $ 9,787,657 | $ 6,734,496
Weighted-average prepayment speed (CPR) | 14.07% | 10.05%
Estimated impact on fair value of a 10% increase | $ (4,493) | $ (2,839)
Estimated impact on fair value of a 20% increase | $ (8,599) | $ (5,474)
Discount rate | 11.49% | 9.68%
Estimated impact on fair value of a 100 bp increase | $ (2,942) | $ (3,086)
Estimated impact on fair value of a 200 bp increase | $ (5,674) | $ (5,932)
Weighted-average coupon interest rate | 3.58% | 4.20%
Weighted-average servicing fee (basis points) | 0.28% | 0.29%
Weighted-average remaining maturity (in months) | 328 months | 335 months

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- Definition Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of one percent adverse change in discount rate. + References No definition available. + Details
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- Definition Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of two percent adverse change in discount rate. + References No definition available. + Details
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- Definition Servicing assets and servicing liabilities at fair value assumptions used to estimate fair value weighted average coupon interest rate. + References No definition available. + Details
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- Definition Servicing assets and servicing liabilities at fair value assumptions used to estimate fair value weighted average servicing fee. + References No definition available. + Details
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- Definition Weighted average life of securitized assets regardless of when the transfer occurred, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719 + Details
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- Definition Discount rate which is used to value residual cash flows generated by financial assets of a securitization, asset-backed financing arrangement, or similar transfer regardless of when the transfer occurred. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719 + Details
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- Definition Estimated rate of prepayment of principal on financial assets regardless of when the transfer occurred. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719 + Details
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- Definition Principal amount of transferred financial assets in which the transferor has continuing involvement with the assets underlying the transaction. Continuing involvement includes, but is not limited to, servicing, recourse, and restrictions on transferor's interests in transferred financial assets. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719 + Details
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- Definition The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719 + Details
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- Definition The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719 + Details
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